Process and machine for producing metal alloy components

ABSTRACT

Machine for making metal alloy components through moulding comprising a lower half-mould and an upper half-mould that can be coupled with each other so as to form the shape of at least one of said metal alloy components, a device for supplying the molten alloy in said lower half-mould. Said lower half-mould comprises a pair of identical impressions that communicate with each other through a central channel, so that said supply device fills both of the impressions with a single cast.

The present invention refers to a process and machine for producing metal alloy components.

In particular, the invention concerns a “direct squeeze casting” type process in which said components are produced through a casting process of the molten alloy in a mould reproducing the shape of said component and subsequent solidification of the alloy, through exerting a continuous pressure on said mould.

Patent application EP 0423447 describes a process and an apparatus for controlling the pressure of the molten metal in a mould.

An example of such components produces according to the process of the present invention are toecaps for accident prevention shoes, made from aluminium or aluminium alloys. Other possible components that can be made are saucepan parts, aluminium window frame components, horseshoes, etc.

Such toecaps must be made so as to withstand an impact test of a force of 200 joules established by a known standard.

To pass such a test, the toe must have characteristics of strength and homogeneity that can only be achieved with a very precise process for making them in which the material inserted in the mould must be accurately dosed.

One of the main problems of the “squeeze casting” method is, indeed, the dosing of the material to be inserted into the mould. Indeed, the Applicant has observed that in known processes it is difficult to exactly dose the amount of material necessary to make a component with the foreseen characteristics.

A further problem of known processes is the distribution of the material in the mould during the process of pressing the male part in the mould itself. Indeed, during pressing the material, in the case of overdosing, would tend to come out from the mould, whereas in the case of underdosing, the component produced would have dishomogeneity that could lead to the failure of the aforementioned strength test.

Last but not least, in the case of production of toe-caps for accident prevention shoes, a problem of known processes is that of making a plurality of toe-caps that are all homogeneous with respect to each other. Such homogeneity can only be achieved if the aforementioned dosing of the material in the mould is carried out with precision.

The Applicant has solved such problems by carrying out a process and a machine for making components made from aluminium or its alloys in which the dosing step of the material in the moulds takes place simultaneously in at least two impressions of the mould, so as to obtain self-levelling.

Moreover the process according to the present invention, during the pressing of he male part or upper half-mould, carries out the controlled recovery of at least part of the molten material that tends to come out from the lower half-mould through said pressing, so as to make a component having a suitable and correctly distributed amount of alloy. The machine also comprises a compensation and recovery device of the excess material cast in the lower half-mould during the moulding step of the component.

An aspect of the present invention concerns a process for producing metal alloy components comprising the following steps:

-   -   casting an amount of molten metal alloy in a lower half-mould         comprising at least a pair of impressions having the same shape         and arranged mirroring each other connected together by a         central channel,     -   moving an upper half-mould in the direction of said lower         half-mould,     -   recovering a predetermined amount of molten metal alloy coming         out from said lower half-mould during the closing step of the         mould,     -   closing the upper half-mould on said lower half-mould and         moulding said component,     -   removing the component realized in the mould.

A further aspect of the present invention concerns a machine for making, by moulding, metal alloy components comprising a lower half-mould and an upper half-mould that can be coupled together so as to form the shape of at least one of said metal alloy components, and a device for supplying the molten alloy into said lower half-mould. Said lower half-mould comprises a pair of identical impressions that communicate with each other through a central channel, so that said supply device fills both of the impressions with a single cast.

The characteristics and the advantages of the process according to the present invention shall become clearer from the following description, given as an example and not for limiting purposes, of an embodiment with reference to the attached figures in which:

FIG. 1 schematically illustrates a machine for producing metal alloy components, in particular for moulding toecaps for accident prevention shoes, in open position according to the present invention;

FIG. 2 schematically illustrates the machine of FIG. 1 in an intermediate position according to the present invention;

FIG. 3 schematically illustrates the machine of FIG. 1 in a closed position according to the present invention;

FIGS. 4 a and 4 b schematically illustrate enlarged details of FIG. 3, in the joining zone between the upper mould and the lower mould;

FIG. 5 illustrates a toe-cap made through the machine and the process according to the present invention.

With reference to the quoted figures, the machine for making toecaps for accident prevention shoes and the like made from aluminium, its alloys and light alloys in general, according to the present invention, comprises a lower half-mould 2 and an upper half-mould 3, which can, respectively, be associated with a lower press plane 4 and an upper press plane 5.

The two half-moulds can be coupled together, through the relative movement between the upper and lower press planes and, preferably, thanks to the downward movement of the upper press plane, to define an impression.

At the lower half-mould there is a device for supplying the molten metal comprising an anthropomorphic arm 6, from which, through a suitable inlet channel, the molten metal is poured into the lower half-mould.

Said upper press plane comprises a piston 7, the lower end of which is preferably rested on the upper half-mould. Said piston moves along a substantially vertical direction so as to push the upper half-mould inside a recess defined by said lower half-mould, in such a way as to be able to carry out the coupling between the upper half-mould and the lower half-mould after the introduction of the molten metal.

The lower half-mould according to the present invention is made in at least two impressions 21 and 22 arranged mirroring each other so as to make at least a pair of toe-caps for each cast of molten material. Such two impressions communicate with each other in a central zone 23 of the mould, so that the liquid metal cast by said supply device in an impression can also fill the mirroring impression, passing through such a central communication zone 23. In such a way, the level in the two impressions is identical and therefore the amount of material in the two impressions is also substantially identical; such “self-levelling” allows the two toe-caps to be made very similar to each other, which is essential since two toe-caps produced simultaneously can be used on the same pair of shoes.

The machine according to the present invention also comprises a compensation and recovery device of the possible excess material cast in the lower half-mould.

In a first embodiment, such a device includes a hydraulic circuit for the recovery of the molten metal comprising a counter-pressure piston 81 the movement of which is preferably controlled by an oleodynamic circuit. Such an oleodynamic circuit is used to keep a constant pressure on the counter-pressure piston. The oleodynamic circuit comprises a chamber 82 in which said piston is inserted, which is filled with fluid both below and above the piston which is arranged in an intermediate position. The filling of such a chamber is carried out through a pair of supply channels 83 and 84 and by a supply pump 85. Such a pump is suitable for keeping a constant pressure of the fluid in said chamber and therefore a constant pressure on said counter-pressure piston.

Such a hydraulic circuit for the recovery of the molten metal also comprises a recovery channel 86 connected at one of is ends with said piston 81 and at the opposite end being associated with a peripheral portion 87 of said lower half-mould. A portion of molten metal can come out from such a peripheral portion 87 during the moulding operation.

The process for producing metal alloy components according to the present invention is carried out according to the following methods.

The first step (illustrated in particular in FIG. 1) foresees the casting of the molten metal through said supply circuit, in particular through said anthropomorphic arm 6, inside the lower half-mould.

The liquid at least partially fills the two impressions 21 and 22 arranged mirroring each other, and the amount of molten metal poured into one impression is substantially identical to that of the other, since the communication channel 23 allows the passage of liquid between them.

The second step (illustrated in particular in FIG. 2) foresees the closing of the mould taking the upper press plane in contact with the lower press plane.

The third step (illustrated in particular in FIG. 3) foresees the downward movement of the upper half-mould 3 (male part) in the lower half-mould 2 (female part).

During this step, the excess liquid can come out from the mould under the effect of the pressing of the upper half-mould. According to the present invention such excess liquid is channelled inside said recovery channel 86. To obtain a product with suitable characteristics, the excess liquid is calibrated. In particular, it is necessary to control the amount of excess liquid that tends to come out from the lower half-mould and invade the recovery channel. The counter-pressure piston 81 exerts a predetermined pressure on the molten metal or excess liquid suitable for allowing a predetermined amount thereof to come out.

In FIGS. 4 a and 4 b it can be seen how the liquid that comes out from the lower half-mould, in the direction indicated by the arrow F1, is conveyed inside the channel 86. Such a thrust of the liquid tends to make the counter-pressure piston 31 move in the direction indicated by the arrow F2 The movement of such pressure is, however, limited by the pressure of the fluid inside the chamber 82, which allows limited movement of the piston and therefore just a predetermined portion of molten metal to come out from the mould. By acting on the oleodynamic circuit it is possible to determine the suitable amount of molten metal to come out from the mould.

According to an alternative of the present invention, the compensation and recovery device of the possible excess material cast in the mould can comprise just a recovery channel of the excess molten metal.

A further alternative of the present invention foresees that the counter-pressure piston is arranged in the lower press plane, in particular close to the central channel 26, so as to carry out the further function of ejecting the toe-caps from he lower half-mould once the moulding step is complete. In such a configuration, as well as the oleodynamic circuit that controls the thrust of the counter-pressure piston, it is foreseen for there to be a preloaded spring that allows the upward movement of the piston once the upper press plane has been lifted.

After moulding, the toe-caps produced can be treated further, through a solution heat treatment and tempering process suitable for giving them greater strength.

A further treatment that can be carried out on the toe-caps concerns making holes in predetermined positions on them in order to reduce the amount of alloy contained in a toe-cap and in order to aerate the part of the shoe that contains the toe-cap itself. Of course, the holes shall not be made in the parts of the toe-cap that require greater resistance to squashing.

Moreover, the upper half-mould is configured so that during the insertion thereof in the lower half-mould, in an intermediate position, for example like the one highlighted in FIG. 2, the central zone of the upper half-mould is already in contact with the molten metal whilst the mould is not totally closed. This allows the molten metal to partially come out from the mould to contribute to the aforementioned calibration through the counter-pressure piston or through the recovery channel.

The type of alloy used to produce such toe-caps is per se a composition that achieves characteristics suitable for passing the strength tests quoted previously.

A suitable alloy for making such toe-caps, as well as containing aluminium comprises from 3.5 to 4% copper, less than 0.1% silicon, from 0.4 to 0.5% magnesium, from 0.15 to 0.2% titanium and about 0.16% iron.

A toe-cap made according to such a process and using such an alloy has passed the aforementioned impact test. 

1. Process for producing metal alloy components comprising the following steps: casting a predetermined amount of molten metal alloy in a lower half-mould comprising at least a pair of impressions having the same shape and connected together by a central channel, moving an upper half-mould in the direction of said lower half-mould, recovering a predetermined amount of molten metal alloy coming out from said lower half-mould during the closing step of the mould, closing the upper half-mould on said lower half-mould and moulding said component, removing the component realized in the mould.
 2. Process according to claim 1, wherein said recovery step comprises channelling said predetermined amount of alloy, exerting a predetermines counter-pressure on said channel so as to regulate said amount of molten alloy.
 3. Process according to claim 1, further comprising the steps of: solution heat treating the moulded component, tempering the moulded component.
 4. Toe-cap for accident prevention shoes, characterised in that it is made from an aluminiun alloy comprising from 3.5 to 4% copper, less than 0.1% silicon, from 0.4 to 0.5% magnesium, from 0.15 to 0.2% zitanium and about 0.16% iron.
 5. Toe-cap for accident prevention shoes according to claim 4, comprising a plurality of through holes made in predetermined positions of said toe-cap.
 6. Machine for making metal alloy components through moulding comprising a lower half-mould and an upper half-mould that can be coupled with each other so as to form the shape of at least one of said metal alloy components, a device for supplying the molten alloy in said lower half-mould, characterised in that said lower half-mould comprises at least a pair of identical impressions that communicate with each other through a central channel, so that said supply device fills both of the impressions with a single cast.
 7. Machine for making metal alloy components through moulding comprising a lower half-mould and an upper half-mould that can be coupled with each other so as to form the shape of at least one of said metal alloy components, a device for supplying the molten alloy in said lower half-mould, characterised in that it comprises a compensation and recovery device of the possible excess material cast in the lower half-mould during the moulding step of the component.
 8. Machine according to claim 7, wherein said lower half-mould comprises at least a pair of identical impressions that communicate with each other through a central channel, so that said supply device fills both of the impressions with a single cast.
 9. Machine according to claim 7, wherein said compensation device comprises a hydraulic circuit including a counter-pressure piston, a recovery channel, connected at one of its ends with said piston and at the opposite end being associated with a peripheral portion of said logier half-mould.
 10. Machine according to claim 7, wherein the movement of said piston is controlled by an oleodynamic circuit.
 11. Machine according to claim 10, wherein said oleodynamic circuit comprises a chamber in which said piston is inserted, filled with a fluid both above and below the piston through a pair of supply channels and from a supply pump, said piston being arranged in an intermediate position, and such a pimp being suitable for keeping a constant pressure of the fluid in said chamber and a constant pressure on said piston.
 12. Machine according to claim 8, wherein said counter-pressure piston is arranged in the lower press plane close to said central channel, and has a preloaded spring that allows the upward movement of the piston once the upper press plane was been lifted, so as to carry out the function of ejecting the toe-caps from the lower half-mould once the moulding step is complete.
 13. Machine according to claim 7, wherein said compensation and recovery device comprises a recovery channel of the excess molten metal. 